I would like to find a simple alternative to photoshop for creating band flyers. I don't need anything fancy, maybe some basic cropping of pictures and fonts. I already have pages but I don't think it's really what I need to create a nice poster.

Don't laugh, but Keynote is actually great for stuff like that. I use it all the time. Not only does it do the job well, it makes it easy to do things like align and centring your images. Add Preview for a few crops and size adjustments here and there and you have a powerful set of tools at your disposal.